Cardiac transplantation is the ultimate treatment option for patients with end stage heart failure. Cardiac allograft vasculopathy remains a leading cause of morbidity and mortality after transplantation. Angiotensin converting enzyme inhibitors are used in less than one half of transplant recipients. Preliminary data suggest that angiotensin converting enzyme inhibitors retard the atherosclerotic plaque development that is the hallmark of cardiac allograft vasculopathy. Moreover, this class of drug appears to increase circulating endothelial progenitor cell number and has anti-inflammatory properties, both of which improve endothelial dysfunction, the key precursor to the development of cardiac allograft vasculopathy. The objective of this project is to investigate the role of an angiotensin converting enzyme inhibitor, ramipril, in preventing the development of cardiac allograft vasculopathy. During the first month after cardiac transplantation subjects will undergo coronary angiography with intravascular ultrasound measurements of plaque volume in the left anterior descending coronary artery. Using a coronary pressure wire, epicardial artery and microvascular physiology will be assessed. Finally, endothelial function and mediators of endothelial function, including circulating endothelial progenitor cells, will be measured. Subjects will then be randomized in a double blind fashion to either ramipril or placebo. After 1 year, the above assessment will be repeated. The primary endpoint will be the development of cardiac allograft vasculopathy based on intravascular ultrasound-derived parameters. The second aim will be to assess the effect of ramipril on endothelial dysfunction early after transplantation. The final aim is to determine the impact of ramipril on coronary physiology early after transplantation.